Autoradiographic localization of 125I-galanin binding sites in the blowfly brain

Abstract

The localization of porcine galanin (pGAL) binding sites in the brain of the blowfly Phormia terraenovae was investigated by autoradiography using the following radioiodinated ligands: pGAL 1–29 (two isoforms), pGAL 15–29 and rat (r) GAL 1–29. The different porcine radioligands bound specifically with the following intensity: 125I-[Tyr 26]-pGAL15–29⪢ 125I-[Tyr 26]-pGAL1–29⪢ 125I-[Tyr 9]-pGAL1–29. With rat galanin 125I-[Tyr 9]-rGAL1–29 no specific binding could be shown. In addition, displacement of 125I-[Tyr 26]-pGAL1–29 was tested with pGAL 1–29, pGAL 1–22 and pGAL 15–29 (at 0.1 nM–1 μM). A gradual displacement was achieved with increasing concentrations of pGAL 1–29 and pGAL15–29, whereas no displacement with pGAL 1–22 was detected. The results indicate that the C-terminal portion of pGAL is important for binding in the blowfly. The pGAL binding sites were localized in synaptic neuropils of the central body, the antennal lobes, the optic lobes, the pars intercerebralis and the subesophageal ganglion, all of which contain GAL-like immunoreactive neural processes.